Is the Organ Care System (OCS) Still the First Choice With Emerging New Strategies for Donation After Circulatory Death (DCD) in Heart Transplant?

Abstract

The scarcity of donor hearts continues to be a challenge in transplants for advanced heart failure patients. With an increasing number of patients on the waiting list for a heart transplant, the discrepancy in the number between donors and recipients is gradually increasing and poses a new challenge that plagues the healthcare systems when it comes to the heart. Several technologies have been developed to expand the donor pool in recent years. One such method is the organ care system (OCS). The standard method of organ preservation is the static cold storage (SCS) method which allows up to four hours of safe preservation of the heart. However, beyond four hours of cold ischemia, the incidence of primary graft dysfunction increases significantly. OCS keeps the heart perfused close to the physiological state beyond the four hours with superior results, which allows us to travel further and longer distances, leading to expansion in the donor pool. In this review, we discuss the OCS system, its advantages, and shortcomings.

Keywords: cold ischemic time; donation after circulatory death (dcd); donor pool expansion; heart transplant; organ care system; organ preservation.

Figure 1. This Figure illustrates an Organ Care System (OCS) heart machine on the left with the schematic diagram on the right, breaking down the processes involved.

The aorta is connected to the aortic line, the pulmonary artery is connected to the pulmonary artery line (PA line), the left atrium is opened, and the left ventricle is vented via a left ventricle vent (LV vent ). The superior and inferior vena cava are ligated. Blood from the PA line and LV vent goes to the reservoir and is pumped to the gas exchanger where it is oxygenated, passed through a warmer, and returned to the heart through the aortic line. The blood pressure, SpO2 (oxygen saturation), and flow rate are all measured during the blood circulation through the different lines. This ensures that the heart receives continuous blood circulation, and all the parameters of the heart are continuously monitored and maintained within narrow margins.

Figure 2. Figure shows the setup (A) and display (B) of a TransMedics Organ Care System (OCS) illustrating all the parameters of the heart that are continuously monitored.

The parameters being monitored include aortic pressure (AoP), coronary flow (CF), heart rate (HR), pump flow (PF), hematocrit (HCT), mixed venous oxygen saturation percentage (SvO2), blood temperature, and lactate level. These parameters help the transplant surgeons to monitor the heart continuously and make an informed decision on the viability of the marginalized heart before transplanting it into the recipient.

Figure 3. Figure illustrates the steps of the institution of myocardial perfusion on the OCS machine.

The heart is placed with the left ventricle (LV) facing anteriorly and an LV vent is placed and sutured to the left atrial wall (A). after the heart starts beating, pacing wires are placed (B). After connecting the pulmonary venous cannula to its respective spout and leaving the left ventricular vent free in the tray (C), the heart is covered with sterile plastic covering and the transparent lid of the OCS (Organ Care System) tray is closed (D).